Electric hot plate



July 11, 1967 J. w. JACOBS ELECTRIC HOT PLATE Filed Sept. 22, 1965 INVENTOR. James W. Jacobs United States Patent Ofihce 3,330,939 ELECTREC HOT PLATE James W. Jacobs, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Sept. 22, 1965, Ser. No. 489,364 5 Claims. (Cl. 219-449) This invention relates to surface heating units for as-. sociation with electrical ranges or the like and more particularly to surface heating units ofthe infrared type.

Most presently used commercial surface heating units on electrical ranges and the like utilize a sheathed electrical resistance element formed in a spiral configuration that is selectively energizable across a power source to produce a heat output that is primarily transferred to utensils supported on the surface heating unit through direct conductive heat transfer. While these units are suitable for their intended purpose, they, in many cases, fail to evenly contact the utensils supported thereon so that the heat transfer by conduction is materially reduced. Furthermore, such units require a substantial time period in order to heat up sufiiciently to warm a utensil supported thereon. In certain of these units a speed heat cycle of operation is provided wherein a high energy input is directed through the electrical resistance element for producing a transitory rapid temperature increase in the resistance element to bring the unit up to temperature.

An object of the present invention is to improve surface heating units for ranges or the like by the provision of a surface unit that includes an unsheathed electrical resistance element energizable into an elevated temperature range and disposed with respect to a utensil or the like for transferring heat thereto primarily by infrared radiation in contrast to direct conductive heat transfer wherein the resistance element is formed into a plurality of segments one of which is pulsatingly energized to produce a primary energy output from the surface unit, another of which is energized during a predetermined period following initial energization of the unit to effect a speed heat period of operation and still another of the filaments being continuously energized to damp out visible light pulsations from the other operative resistance elements in the structure.

Further objects and advantages of the present invention willbe apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a view in perspective of an electrical range including a'surface heater unit of the present invention; and

FIGURE 2 is an enlarged view in vertical section taken along the line 2-2 of FIGURE 1 and including an associated diagrammatically illustrated electrical control circuit. 1

Referring now to the drawing, in FIGURE 1, an electrical range is illustrated including a top surface 12 having a plurality of openings 14 therein. Within each of the openings 14 is located an infrared surface heating unit 16 including the features of the present invention. Each of the surface heating units 16 is selectively controlled by a controller 18 having a manually actuated knob or control member 26 thereof located on a representatively shown rear control panel 22 of the range 10.

Each of the heating units 16 is more specifically illustrated in FIGURE 2 as including an upper utensil supporting plate 24 of infrared transmissive material that overlies 3,336,939 Patented July ll, 1967 one of the openings 14 and includes a downwardly depending peripheral flange 26 that supportingly engages the upper surface of the top 12 around the opening 14 therein. The unit 16 further includes a support member 28 having an upper edge portion 30 which overlies the top 12 at the opening therein. A depending portion 32 of the support member 28 has a lower portion 34 thereon on which is supported an electrically insulating base 36 of an evacuated glass bulb 38 of infrared transmissive material including a top portion 46 located in close spaced relationship below the upper utensil support plate 24.

The bulb 38 further includes a skirt 42 that is inclined inwardly and downwardly of the top 40 to merge with a sealed neck 44 of the bulb 38 located within the electrically insulated base 36.

Within the evacuated bulb 38 is located a primary high temperature resistance element or filament 46 energizable into a temperature range at which it emits infrared radiation directly upwardly through the top 40 of the bulb 38 and the upper utensil supporting plate 24 and also has infrared radiation therefrom reflected from an infrared reflective surface 48 on the inside of the skirt 42 and neck 44 of the bulb 38 upwardly through the top til-and utensil supporting plate 24. The energy radiating from the resistance element or filament 46 thereby raises the temperature of a utensil on the plate 24 through radiant heat transfer as contrasted to conductive heat transfer as in the case of conventional surface heating elements of the type including a sheathed spirally wound electrical resistance element.

In addition to the primary electrical resistance element 46, a speed heat or flasher resistance element 50 is also disposed within the bulb 38. The resistance element 50 is operative to produce a preliminary heat output from the unit 16 in addition to that emitted by element 46 during a speed heat cycle of operation to be discussed. Additionally, within the bulb 38 is located an illuminating resistance element 52 that, as will be described, is continually energized during the operation of the unit 16 to continuously illuminate the full planar extent of the heating area defined by the upper utensil supporting plate 24.

In the illustrated arrangement and in accordance with certain of the principles of the present invention, the controller 18 for regulating the operation of each of the units 16 is more particularly set forth in FIGURE 2 as including an on-oif switch 54, an energy pulsing switch 56 and a snap-acting switch 58.

When the control knob 20 of the controller 18 is turned to an on position, suitable means such as a rotatable cam 60 will move a contact carrying arm 62 of the switch 54 to close a pair of contacts 64, 66. This completes an energization circuit for the illuminating resistance element 52 from wire L through a conductor 68 across the closed switch 54 thence through a conductor 70 that is electrically connected to a terminal 72 on the insulated base 36 of the bulb 38. From the terminal 72 a lead wire 74 is electrically connected to one side of the illuminating electrical resistance element 52. The opposite side of the resistance element 52 is electrically connected by a conductor 76 which in turn is connected to a lead wire 78 that in turn is electrically connected to a terminal 80 in the base 36. From the terminal 86, the energization circuit of the illuminating resistance element 52 is completed through a conductor 82 connected to wire L The knob 20 is shown representatively as being connected to the energy pulsing switch 56 through a cam 84 that biases a contact carrying arm 86 to move a contact 88 thereon into engagement with a contact 90 on a polymetallic thermally responsive arm 92 which is selectively deflected upon being heated by a heater element 94 of the switch 56. When the switch 56 is closed, an

. energization circuit for the primary resistance element 46 is completed from Wire L through a conductor 96, the pulsatingly opening and closing switch 56 and a conductor 98 that is electrically connected to a terminal 100 on the base 36. A lead wire 102 runs from the terminal 100 to one side of the resistance element 46 which has the opposite side thereof connected by a conductor 104 to the lead wire 78 from whence the energization circuit of the primary heating resistance element 46 is completed through terminal 80 and conductor -82 to wire L The knob 20 additionally is operatively connected to the snap-acting switch 58 by a resetting cam 106 which engages .an arm 108 having one end thereof supported in a pivot block 110 and the opposite end thereof in engagement with a snap-acting spring 112 which has the opposite end thereof in biasing engagement with the end of a polymetallic, thermally responsive contact carrying arm 114 of the switch 58. The snap-acting switch 58 in the illustrated arrangement is shown in an inoperative position following a speed heat operation. The switch '58 is reset by the cam 106 when the knob 20 is moved to an off position whereby .a movable contact 116 on the member 114 is moved into electrical contact with a fixed contact 118. When the contacts 116, 118 are in their reset position, a speed heat circuit through the flasher resistance element 50* is completed from wire L through a conductor 120 thence through a heating element 122 for raising the temperature of the polymetallic member 114 so that following a predetermined period of time constituting the speed heat phase of'operation, the member 114 will deflect sufficiently to overcome the bias of the spring 112 which snaps to separate the contacts 116, 118 and maintain them apart as shown in FIGURE 2.

Initially, however, the energization circuit is completed through the closed contacts of switch 58 thence through a conductor 124 that is electrically connected to a terminal 126 in the base 36. A lead wire 128 from the terminal 126 electrically connects to one side of the resistance element 50 which has the opposite side thereof connected by t a conductor 129 to the lead wire 78 for completing the energization circuit for the element 50 through terminal '80 and conductor 82 back to wire L In the illustrated infrared surface heating unit the primary heating resistance element 46 will continuously pulsate into and out of an elevated temperature range for maintaining a predetermined controlled energy output from the unit 16 as established by the energy pulsing switch 56 of the controller 18 as preset by the manually .actuatable control knob 20. The resistance element 46 hasa high Wettage rating and is self-heated sufficiently to cause a substantial amount of visible light to be directed therefrom through the bulb 38 and the upper utensil supporting plate 24. Since the resistance element 46 is pulsatingly energized, the light produced thereby likewise pulses on and off. The pulsating illumination creates a distraction on the top 12 of the range and accordingly the iluminating resistance element 52 isenergized continuously through the above-described energization circuit to produce a continuous background illumination of the plate 24 that will continually damp out the pulsing light from the primary heating resistance element 46 during its operation.

Additionally, in order to have a speed heat operation when the unit 16 is initially turned on, during which time the unit 16 will produce a substantial heat output in addition to that of the primary heating element 46, the snap-acting switch 58 is operative to continually connect the speed heat or flasher resistance element across the power source to supplement the heat output from the primary resistance element 46 during .a predetermined time period as established by the characteristics of the snap-acting switch 58.

By virtue of the above-described arrangement, an cfficient infrared surface heating unit is produced that has the characteristics of an initial high energy output during a speed heat cycle of operation, a preselectable controlled heat output at a lower energy level during normal energization periods and, in addition, includes means for preventing undesirable light pulsations from the unit during its operation. Furthermore, by the provision of such plural high-energy electrical resistance elements that are located in spaced relationship to a utensil to be heated, and the fact that the energy transfer is effected through radiation rather than during heat transfer by conduct-ion, utensil heating and the like will be quickly and effectively accomplished.

While the embodiment of the present invention as herein disclosed constitutes .a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In an infrared surface heater unit for a range or the like, thecombination of, first, second and third electrical resistance elements energizable into the infrared range, controller means for energizing said surface heater including first switch means for continuously energizing said first resistance element when said surface heating unit is turned on, said controller means including second switch means responsive to initial energization of the surface heating unit for selectively energizing said second resistance element for a predetermined time period following initial energization of the heating unit for producing a speed heat effect following which said second resistance element is continuously de-energized, said con troller means including third switch means for pulsating elements disposed between said upper plate and said reflective surface out of direct conductive heat transfer therewith, a controller for selectively connecting each of said plurality of resistance elements across a power source, said controller including first control means for pulsatinglyenergizing one of said resistance elements into an infrared ern-issive temperature range for producing a radiant energy transfer to utensils supported on said upper plate for raising the temperature of the utensil, said controller including second control means for metering a predetermined amount of energy continuously'to a' second of said resistance elements during a speed heat cycle of operation that is terminated a predetermined period following energization of said heater element, said one of said resistance elements having a pulsing visible light directed therefrom for pulsatingly illuminating said upper utensil supporting plate, said controller including third control means for continuously energizing a third of said plurality of resistance elements for producing a continuous illumination of said upper utensil supporting plate for damping the visible light pulsations from said one of said plurality of resistance elements.

3. In the combination of claim 2, said second controlmeans for energizing saidsecond of said resistance elements during the speed heat cycle of opera-tion including a pair of electrical contacts, a polymetallic element for movably carrying one of said electrical contacts out of electrical contact with the other of said contacts, heater means for deflecting said polymetallic element to establish the period of the speed heat cycle of operation, and

resettable means for maintaining said contacts continuously separated following a predetermined deflection of said polymetallic element.

References Cited UNITED STATES PATENTS 2,419,083 5/1947 Myers 2l9-449 2,804,531 8/1957 Dadson 2l9-452 2,859,368 11/1958 Biggs et al. 219-552 RICHARD M. WOOD, Primary Examiner. L. H. BENDER, Assistant Examiner. 

1. IN AN INFRARED SURFACE HEATER UNIT FOR A RANGE OR THE LIKE, THE COMBINATION OF, FIRST, SECOND AND THIRD ELECTRICAL RESISTANCE ELEMENTS ENERGIZABLE INTO THE INFRARED RANGE, CONTROLLER MEANS FOR ENERGIZING SAID SURFACE HEATER INCLUDING FIRST SWITCH MEANS FOR CONTINUOUSLY ENERGIZING SAID FIRST RESISTANCE ELEMENT WHEN SAID SURFACE HEATING UNIT IS TURNED ON, SAID CONTROLLER MEANS INCLUDING SECOND SWITCH MEANS RESPONSIVE TO INITIAL ENERGIZATION OF THE SURFACE HEATING UNIT FOR SELECTIVELY ENERGIZING SAID SECOND RESISTANCE ELEMENT FOR A PREDETERMINED TIME PERIOD FOLLOWING INITIAL ENERGIZATION OF THE HEATING UNIT FOR PRODUCING A SPEED HEAT EFFECT FOLLOWING WHICH SAID SECOND RESISTANCE ELEMENT IS CONTINUOUSLY DE-ENERGIZED, SAID CONTROLLER MEANS INCLUDING THIRD SWITCH MEANS FOR PULSATINGLY ENERGIZING SAID THIRD RESISTANCE ELEMENT DURING THE CON- 